Antioxidant and antimicrobial activities of ethanol and aqueous extracts from Urtica urens

Urtica urens L. (Urticaceae) is an important and commonly used plant for its medicinal and pharmacological properties.

We analyzed the antioxidant and antimicrobial activities of the leaves of Urtica urens in ethanol (EtOH) and water (WA) solvents, employing standard analytical methods.

Polyphenol, flavonoid and tannin content of Urtica urens leaves were determined, after their extraction, using EtOH (70%) and WA extracts as well as the antioxidant (DPPH, ABTS, β-carotene and FRAP) and the antibacterial (via the method of dilution tests) activities of EtOH and WA extracts.

The 70% EtOH of Urtica urens showed the highest values of total phenolic (31.41 mg GAE/g DW), flavonoids (6.81 mg quercetin/g DW), tannin (8.29 mg GAE/g DW) and TEAC (560 mmol Trolox/g DW), compared to the WA. The results of DPPH for EtOH (95.56%) were higher than that of WA (64.56%) at a concentration of 40 mg/L. The extracts displayed a FRAP 106.23 for EtOH and 30.55 μmol Fe(II)/g DW for WA. The results clearly indicated that EtOH was the strongest radical scavenger (IC₅₀=245.65 ± 10.2 μg/mL). Ethanol was the most effective with minimum inhibitory concentration (MIC) < 250 μg/mL. WA has no antibacterial activity.

The results indicate that leaves of Urtica urens could be used as natural antioxidant and antimicrobial agents.